Root system architecture change in response to waterlogging stress in a 448 global collection of rapeseeds (Brassica napus L.).

MAIN CONCLUSIONS: A novel image-based screening method for precisely identifying genotypic variations in rapeseed RSA under waterlogging stress was developed. Five key root traits were confirmed as good indicators of waterlogging and might be employed in breeding, particularly when using the MFVW approach. Waterlogging is a vital environmental factor that has detrimental effects on the growth and development of rapeseed (Brassica napus L.). Plant roots suffer from hypoxia under waterlogging, which ultimately confers yield penalty. Therefore, it is crucially important to understand the genetic variation of root system architecture (RSA) in response to waterlogging stress to guide the selection of new tolerant cultivars with favorable roots. This research was conducted to investigate RSA traits using image-based screening techniques to better understand how RSA changes over time during waterlogging at the seedling stage. First, we performed a t-test by comparing the relative root trait value between four tolerant and four sensitive accessions. The most important root characteristics associated with waterlogging tolerance at 12 h are total root length (TRL), total root surface area (TRSA), total root volume (TRV), total number of tips (TNT), and total number of forks (TNF). The root structures of 448 rapeseed accessions with or without waterlogging showed notable genetic diversity, and all traits were generally restrained under waterlogging conditions, except for the total root average diameter. Additionally, according to the evaluation and integration analysis of 448 accessions, we identified that five traits, TRL, TRSA, TRV, TNT, and TNF, were the most reliable traits for screening waterlogging-tolerant accessions. Using analysis of the membership function value (MFVW) and D-value of the five selected traits, 25 extremely waterlogging-tolerant materials were screened out. Waterlogging significantly reduced RSA, inhibiting root growth compared to the control. Additionally, waterlogging increased lipid peroxidation, accompanied by a decrease in the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). This study effectively improves our understanding of the response of RSA to waterlogging. The image-based screening method developed in this study provides a new scientific guidance for quickly examining the basic RSA changes and precisely predicting waterlogging-tolerant rapeseed germplasms, thus expanding the genetic diversity of waterlogging-tolerant rapeseed germplasm available for breeding.

A new chromosome-scale genome of wild Brassica oleracea provides insights into the domestication of Brassica crops.

The cultivated diploid Brassica oleracea is an important vegetable crop, but the genetic basis of its domestication remains largely unclear in the absence of high-quality reference genomes of wild B. oleracea. Here, we report the first chromosome-level assembly of the wild Brassica oleracea L. W03 genome (total genome size, 630.7 Mb; scaffold N50, 64.6 Mb). Using the newly assembled W03 genome, we constructed a gene-based B. oleracea pangenome and identified 29 744 core genes, 23 306 dispensable genes, and 1896 private genes. We re-sequenced 53 accessions, representing six potential wild B. oleracea progenitor species. The results of the population genomic analysis showed that the wild B. oleracea populations had the highest level of diversity and represents the most closely related population to modern-day horticultural B. oleracea. In addition, the WUSCHEL gene was found to play a decisive role in domestication and to be involved in cauliflower and broccoli curd formation. We also illustrate the loss of disease-resistance genes during selection for domestication. Our results provide new insights into the domestication of B. oleracea and will facilitate the future genetic improvement of Brassica crops.

Superhydrophobic Pseudosupertetrahedral Sulfido Metalate Clusters for Constructing Liquid Marbles.

One pseudopentasupertetrahedral chalcogenidometalate cluster, [(BuSn)3SnCd4S13(OH)]·6(H+DMP) (PPS-1; H+DMP = protonated 3,5-dimethylpiperidine), has been isolated by use of an organotin precursor. They are arranged to generate two types of tetrahedrally patterned cages, which further interconnect to form a diamond network. Owing to the covalent attachment of abundant alkyl groups, PPS-1 exhibits excellent hydrophobicity and could be used as an assembly substance for building liquid marbles.

Research Progress on the Effect of Nitrogen on Rapeseed between Seed Yield and Oil Content and Its Regulation Mechanism.

Rapeseed (Brassica napus L.) is one of the most important oil crops in China. Improving the oil production of rapeseed is an important way to ensure the safety of edible oil in China. Oil production is an important index that reflects the quality of rapeseed and is determined by the oil content and yield. Applying nitrogen is an important way to ensure a strong and stable yield. However, the seed oil content has been shown to be reduced in most rapeseed varieties after nitrogen application. Thus, it is critical to screen elite germplasm resources with stable or improved oil content under high levels of nitrogen, and to investigate the molecular mechanisms of the regulation by nitrogen of oil accumulation. However, few studies on these aspects have been published. In this review, we analyze the effect of nitrogen on the growth and development of rapeseed, including photosynthetic assimilation, substance distribution, and the synthesis of lipids and proteins. In this process, the expression levels of genes related to nitrogen absorption, assimilation, and transport changed after nitrogen application, which enhanced the ability of carbon and nitrogen assimilation and increased biomass, thus leading to a higher yield. After a crop enters the reproductive growth phase, photosynthates in the body are transported to the developing seed for protein and lipid synthesis. However, protein synthesis precedes lipid synthesis, and a large number of photosynthates are consumed during protein synthesis, which weakens lipid synthesis. Moreover, we suggest several research directions, especially for exploring genes involved in lipid and protein accumulation under nitrogen regulation. In this study, we summarize the effects of nitrogen at both the physiological and molecular levels, aiming to reveal the mechanisms of nitrogen regulation in oil accumulation and, thereby, provide a theoretical basis for breeding varieties with a high oil content.

Research Progress in High-Efficiency Utilization of Nitrogen in Rapeseed.

Nitrogen (N) is one of the most important mineral elements for plant growth and development and a key factor for improving crop yield. Rapeseed, Brassica napus, is the largest oil crop in China, producing more than 50% of the domestic vegetable oil. However, high N fertilizer input with low utilization efficiency not only increases the production cost but also causes serious environmental pollution. Therefore, the breeding of rapeseed with high N efficiency is of great strategic significance to ensure the security of grain and oil and the sustainable development of the rapeseed industry. In order to provide reference for genetic improvement of rapeseed N-efficient utilization, in this article, we mainly reviewed the recent research progress of rapeseed N efficiency, including rapeseed N efficiency evaluation, N-efficient germplasm screening, and N-efficient physiological and molecular genetic mechanisms.

Whole-Genome Comparison Reveals Structural Variations behind Heading Leaf Trait in Brassica oleracea.

Brassica oleracea displays remarkable morphological variations. It intrigued researchers to study the underlying cause of the enormous diversification of this organism. However, genomic variations in complex heading traits are less known in B. oleracea. Herein, we performed a comparative population genomics analysis to explore structural variations (SVs) responsible for heading trait formation in B. oleracea. Synteny analysis showed that chromosomes C1 and C2 of B. oleracea (CC) shared strong collinearity with A01 and A02 of B. rapa (AA), respectively. Two historical events, whole genome triplication (WGT) of Brassica species and differentiation time between AA and CC genomes, were observed clearly by phylogenetic and Ks analysis. By comparing heading and non-heading populations of B. oleracea genomes, we found extensive SVs during the diversification of the B. oleracea genome. We identified 1205 SVs that have an impact on 545 genes and might be associated with the heading trait of cabbage. Overlapping the genes affected by SVs and the differentially expressed genes identified by RNA-seq analysis, we identified six vital candidate genes that may be related to heading trait formation in cabbage. Further, qRT-PCR experiments also verified that six genes were differentially expressed between heading leaves and non-heading leaves, respectively. Collectively, we used available genomes to conduct a comparison population genome analysis and identify candidate genes for the heading trait of cabbage, which provides insight into the underlying reason for heading trait formation in B. oleracea.

Genome-Wide Identification and Functional Characterization of Stress Related Glyoxalase Genes in Brassica napus L.

Rapeseed (Brassica napus L.) is not only one of the most important oil crops in the world, but it is also an important vegetable crop with a high value nutrients and metabolites. However, rapeseed is often severely damaged by adverse stresses, such as low temperature, pathogen infection and so on. Glyoxalase I (GLYI) and glyoxalase II (GLYII) are two enzymes responsible for the detoxification of a cytotoxic metabolite methylglyoxal (MG) into the nontoxic S-D-lactoylglutathione, which plays crucial roles in stress tolerance in plants. Considering the important roles of glyoxalases, the GLY gene families have been analyzed in higher plans, such as rice, soybean and Chinese cabbage; however, little is known about the presence, distribution, localizations and expression of glyoxalase genes in rapeseed, a young allotetraploid. In this study, a total of 35 BnaGLYI and 30 BnaGLYII genes were identified in the B. napus genome and were clustered into six and eight subfamilies, respectively. The classification, chromosomal distribution, gene structure and conserved motif were identified or predicted. BnaGLYI and BnaGLYII proteins were mainly localized in chloroplast and cytoplasm. By using publicly available RNA-seq data and a quantitative real-time PCR analysis (qRT-PCR), the expression profiling of these genes of different tissues was demonstrated in different developmental stages as well as under stresses. The results indicated that their expression profiles varied among different tissues. Some members are highly expressed in specific tissues, BnaGLYI11 and BnaGLYI27 expressed in flowers and germinating seed. At the same time, the two genes were significantly up-regulated under heat, cold and freezing stresses. Notably, a number of BnaGLY genes showed responses to Plasmodiophora brassicae infection. Overexpression of BnGLYI11 gene in Arabidopsis thaliana seedlings confirmed that this gene conferred freezing tolerance. This study provides insight of the BnaGLYI and BnaGLYII gene families in allotetraploid B. napus and their roles in stress resistance, and important information and gene resources for developing stress resistant vegetable and rapeseed oil.

High-throughput multiplex cpDNA resequencing clarifies the genetic diversity and genetic relationships among Brassica napus, Brassica rapa and Brassica oleracea.

Brassica napus (rapeseed) is a recent allotetraploid plant and the second most important oilseed crop worldwide. The origin of B. napus and the genetic relationships with its diploid ancestor species remain largely unresolved. Here, chloroplast DNA (cpDNA) from 488 B. napus accessions of global origin, 139 B. rapa accessions and 49 B. oleracea accessions were populationally resequenced using Illumina Solexa sequencing technologies. The intraspecific cpDNA variants and their allelic frequencies were called genomewide and further validated via EcoTILLING analyses of the rpo region. The cpDNA of the current global B. napus population comprises more than 400 variants (SNPs and short InDels) and maintains one predominant haplotype (Bncp1). Whole-genome resequencing of the cpDNA of Bncp1 haplotype eliminated its direct inheritance from any accession of the B. rapa or B. oleracea species. The distribution of the polymorphism information content (PIC) values for each variant demonstrated that B. napus has much lower cpDNA diversity than B. rapa; however, a vast majority of the wild and cultivated B. oleracea specimens appeared to share one same distinct cpDNA haplotype, in contrast to its wild C-genome relatives. This finding suggests that the cpDNA of the three Brassica species is well differentiated. The predominant B. napus cpDNA haplotype may have originated from uninvestigated relatives or from interactions between cpDNA mutations and natural/artificial selection during speciation and evolution. These exhaustive data on variation in cpDNA would provide fundamental data for research on cpDNA and chloroplasts.

Characterization of FAE1 in the zero erucic acid germplasm of Brassica rapa L.

The modification of erucic acid content in seeds is one of the major goals for quality breeding in oil-yielding Brassica species. However, few low erucic acid (LEA) resources are available, and novel LEA genetic resources are being sought. Fatty acid elongase 1 (FAE1) is the key gene that controls erucic acid synthesis. However, the mechanism for erucic acid synthesis in B. rapa lacks systematic study. Here, we isolated zero erucic acid lines from 1981 Chinese landraces of B. rapa and found that the formation of LEA is not attributable to variations in FAE1 coding sequences, as reported for B. napus, but may be attributable to the decrease in FAE1 expression. Moreover, the FAE1 promoter sequences of LEA and high erucic acid materials shared 95% similarity. Twenty-eight bases deletions (containing a 24-base AT-rich region) were identified approximately 1300 bp upstream from the FAE1 start codon in the LEA accessions. The genotype with the deletions co-segregated with the LEA trait in the segregating population. This study isolated an LEA B. rapa resource that can be exploited in Brassica cultivation. The promoter variations might modify the expression level of FAE1, and the results shed light on novel regulation mechanisms for erucic acid synthesis.

Genome-wide investigation of genetic changes during modern breeding of Brassica napus.

KEY MESSAGE: Considerable genome variation had been incorporated within rapeseed breeding programs over past decades. In past decades, there have been substantial changes in phenotypic properties of rapeseed as a result of extensive breeding effort. Uncovering the underlying patterns of allelic variation in the context of genome organisation would provide knowledge to guide future genetic improvement. We assessed genome-wide genetic changes, including population structure, genetic relatedness, the extent of linkage disequilibrium, nucleotide diversity and genetic differentiation based on F ST outlier detection, for a panel of 472 Brassica napus inbred accessions using a 60 k Brassica Infinium® SNP array. We found genetic diversity varied in different sub-groups. Moreover, the genetic diversity increased from 1950 to 1980 and then remained at a similar level in China and Europe. We also found ~6-10 % genomic regions revealed high F ST values. Some QTLs previously associated with important agronomic traits overlapped with these regions. Overall, the B. napus C genome was found to have more high F ST signals than the A genome, and we concluded that the C genome may contribute more valuable alleles to generate elite traits. The results of this study indicate that considerable genome variation had been incorporated within rapeseed breeding programs over past decades. These results also contribute to understanding the impact of rapeseed improvement on available genome variation and the potential for dissecting complex agronomic traits.

Comparison of the heat stress induced variations in DNA methylation between heat-tolerant and heat-sensitive rapeseed seedlings.

DNA methylation is responsive to various biotic and abiotic stresses. Heat stress is a serious threat to crop growth and development worldwide. Heat stress results in an array of morphological, physiological and biochemical changes in plants. The relationship between DNA methylation and heat stress in crops is relatively unknown. We investigated the differences in methylation levels and changes in the cytosine methylation patterns in seedlings of two rapeseed genotypes (heat-sensitive and heat-tolerant) under heat stress. Our results revealed that the methylation levels were different between a heat-tolerant genotype and a heat-sensitive one under control conditions. Under heat treatment, methylation increased more in the heat-sensitive genotype than in the heat-tolerant genotype. More DNA demethylation events occurred in the heat-tolerant genotype, while more DNA methylation occurred in the heat-sensitive genotype. A large and diverse set of genes were affected by heat stress via cytosine methylation changes, suggesting that these genes likely play important roles in the response and adaption to heat stress in Brassica napus L. This study indicated that the changes in DNA methylation differed between heat-tolerant and heat-sensitive genotypes of B. napus in response to heat stress, which further illuminates the molecular mechanisms of the adaption to heat stress in B. napus.

Assessing and broadening genetic diversity of a rapeseed germplasm collection.

Assessing the level of genetic diversity within a germplasm collection contributes to evaluating the potential for its utilization as a gene pool to improve the performance of cultivars. In this study, 45 high-quality simple sequence repeat (SSR) markers were screened and used to estimate the genetic base of a world-wide collection of 248 rapeseed (Brassica napus) inbred lines. For the whole collection, the genetic diversity of A genome was higher than that of C genome. The genetic diversity of C genome for the semi-winter type was the lowest among the different germplasm types. Because B. oleracea is usually used to broaden the genetic diversity of C genome in rapeseed, we evaluated the potential of 25 wild B. oleracea lines. More allelic variations and a higher genetic diversity were observed in B. oleracea than in rapeseed. One B. oleracea line and one oilseed B. rapa line were used to generate a resynthesized Brassica napus line, which was then crossed with six semi-winter rapeseed cultivars to produce 7 F1 hybrids. Not only the allele introgression but also mutations were observed in the hybrids, resulting in significant improvement of the genetic base.

Progress on Salt Tolerance in Brassica napus.

In China, saline-alkali lands constitute 5.01% of the total land area, having a significant impact on both domestic and international food production. Rapeseed (Brassica napus L.), as one of the most important oilseed crops in China, has garnered considerable attention due to its potential adaptability to saline conditions. Breeding and improving salt-tolerant varieties is a key strategy for the effective utilization of saline lands. Hence, it is important to conduct comprehensive research into the adaptability and salt tolerance mechanisms of Brassica napus in saline environments as well as to breed novel salt-tolerant varieties. This review summarizes the molecular mechanism of salt tolerance, physiological and phenotypic indexes, research strategies for the screening of salt-tolerant germplasm resources, and genetic engineering tools for salt stress in Brassica napus. It also introduces various agronomic strategies for applying exogenous substances to alleviate salt stress and provide technological tools and research directions for future research on salt tolerance in Brassica napus.

Genomic selection and genetic architecture of agronomic traits during modern rapeseed breeding.

Rapeseed (Brassica napus L.) is an important oil-producing crop for the world. Its adaptation, yield and quality have been considerably improved in recent decades, but the genomic basis underlying successful breeding selection remains unclear. Hence, we conducted a comprehensive genomic assessment of rapeseed in the breeding process based on the whole-genome resequencing of 418 diverse rapeseed accessions. We unraveled the genomic basis for the selection of adaptation and agronomic traits. Genome-wide association studies identified 628 associated loci-related causative candidate genes for 56 agronomically important traits, including plant architecture and yield traits. Furthermore, we uncovered nonsynonymous mutations in plausible candidate genes for agronomic traits with significant differences in allele frequency distributions across the improvement process, including the ribosome recycling factor (BnRRF) gene for seed weight. This study provides insights into the genomic basis for improving rapeseed varieties and a valuable genomic resource for genome-assisted rapeseed breeding.

Construction of a Bacillus thuringiensis engineered strain with high toxicity and broad pesticidal spectrum against coleopteran insects.

A newly engineered strain, denominated BIOT185, was constructed through integrating the cry8Ca2 gene into the endogenous plasmid of BT185 (contains cry8Ea1) by homologous recombination. The thermosensitive plasmid vector was eliminated by the rising temperature of recombinant cultures. No antibiotic gene or other unnecessary genes were introduced to the new strain. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis demonstrated that the cry8Ca2 gene was expressed normally and produced a 130-kDa protein in the BIOT185 strain. Bioassay results showed that the new strain had high toxicity to the pests Anomala corpulenta and Holotrichia parallela, which often damage the same fields.

Metabolic syndrome and the incidence of knee osteoarthritis: A meta-analysis of prospective cohort studies.

BACKGROUND: Cross-sectional studies suggest an association between metabolic syndrome (MetS) and knee osteoarthritis (KOA). We performed a meta-analysis to evaluate whether MetS is an independent risk factor for KOA. METHODS: Prospective cohort studies evaluating the association between MetS and KOA in general population were retrieved from PubMed and Embase. Only studies with multivariate analyses were included. Data were pooled with a random-effect model, which is considered to incorporate heterogeneity among the included studies. RESULTS: Five studies including 94,965 participants were included, with 18,990 people with MetS (20.0%). With a mean follow-up duration of 14.5 years, 2,447 KOA cases occurred. Pooled results showed that MetS was not significant associated with an increased risk of KOA after controlling of factors including body mass index (adjusted risk ratio [RR]: 1.06, 95% CI: 0.92~1.23, p = 0.40; I2 = 33%). Subgroup analysis showed that MetS was independently associated with an increased risk of severe KOA that needed total knee arthroplasty (RR = 1.16, 95% CI: 1.03~1.30, p = 0.02), but not total symptomatic KOA (RR = 0.84, 95% CI: 0.65~1.08, p = 0.18). Stratified analyses suggested that MetS was independently associated with an increased risk of KOA in women (RR = 1.23, 95% CI: 1.03~1.47, p = 0.02), but not in men (RR = 0.90, 95% CI: 0.70~1.14, p = 0.37). CONCLUSIONS: Current evidence from prospective cohort studies did not support MetS was an independent risk factor of overall KOA in general population. However, MetS may be associated with an increased risk of severe KOA in general population, or overall KOA risk in women.

Characterization of Two Novel Bacillus thuringiensis Cry8 Toxins Reveal Differential Specificity of Protoxins or Activated Toxins against Chrysomeloidea Coleopteran Superfamily.

Scarabaeoidea and Chrysomeloidea insects are agriculture-destructive coleopteran pests. Few effective Bacillus thuringiensis (Bt) insecticidal proteins against these species have been described. Bt isolate BtSU4 was found to be active against coleopteran insects. Genome sequencing revealed two new cry8 genes in BtSU4, designated as cry8Ha1 and cry8Ia1. Both genes expressed a 135 kDa protoxin forming irregular shape crystals. Bioassays performed with Cry8Ha1 protoxin showed that it was toxic to both larvae and adult stages of Holotrichia parallela, also to Holotrichia oblita adults and to Anoplophora glabripennis larvae, but was not toxic to larval stages of H. oblita or Colaphellus bowringi. The Cry8Ia1 protoxin only showed toxicity against H. parallela larvae. After activation with chymotrypsin, the Cry8Ha1 activated toxin lost its insecticidal activity against H. oblita adults and reduced its activity on H. parallela adults, but gained toxicity against C. bowringi larvae, a Chrysomeloidea insect pest that feeds on crucifer crops. The chymotrypsin activated Cry8Ia1 toxin did not show toxicity to any one of these insects. These data show that Cry8Ha1 and Cry8Ia1 protoxin and activated toxin proteins have differential toxicity to diverse coleopteran species, and that protoxin is a more robust protein for the control of coleopteran insects.

Characterization of a novel cry8 gene specific to Melolonthidae pests: Holotrichia oblita and Holotrichia parallela.

A new polymerase chain reaction-restriction fragment length polymorphism method for the identification of cry8-type genes from Bacillus thuringiensis has been established by designing a pair of new universal primers. By this method, a novel gene, cry8Ga1, encoding a polypeptide of 1,157 amino acids with a deduced molecular mass of 131.2 kDa was identified and cloned from B. thuringiensis HBF-18. Recombinant B. thuringiensis strain HD8G, harboring cry8Ga1, has insecticidal activity against larvae of Melolonthidae pests: Holotrichia oblita and Holotrichia parallela. This is the first report of a Cry toxin that has insecticidal activity to Melolonthidae pest H. oblita.

Genome-wide analysis and expression profiles of glyoxalase gene families in Chinese cabbage (Brassica rapa L).

The glyoxalase pathway is composed of glyoxalase I (GLYI) and glyoxalase II (GLYII) and is responsible for the detoxification of a cytotoxic metabolite methylglyoxal (MG) into the nontoxic S-D-lactoylglutathione. The two glyoxalase enzymes play a crucial role in stress tolerance in various plant species. Recently, the GLY gene families have well been analyzed in Arabidopsis, rice and soybean, however, little is known about them in Chinese cabbage (Brassica rapa). Here, 16 BrGLYI and 15 BrGLYII genes were identified in the B. rapa genome, and the BrGLYI and BrGLYII proteins were both clustered into five subfamilies. The classifications, chromosomal distributions, gene duplications, exon-intron structures, localizations, conserved motifs and promoter cis-elements were also predicted and analyzed. In addition, the expression pattern of these genes in different tissues and their response to biotic and abiotic stresses were analyzed using publicly available data and a quantitative real-time PCR analysis (RT-qPCR). The results indicated that the expression profiles of BrGLY genes varied among different tissues. Notably, a number of BrGLY genes showed responses to biotic and abiotic stress treatments, including Plasmodiophora brassicae infection and various heavy metal stresses. Taken together, this study identifies BrGLYI and BrGLYII gene families in B. rapa and offers insight into their roles in plant development and stress resistance, especially in heavy metal stress tolerance and pathogen resistance.

An Integration of Genome-Wide Association Study and Gene Co-expression Network Analysis Identifies Candidate Genes of Stem Lodging-Related Traits in Brassica napus.

Lodging is a persistent problem which severely reduce yield and impair seed quality in rapeseed (Brassica napus L.). Enhancing stem strength (SS) has proven to be an effective approach to decrease lodging risk. In the present study, four interrelated stem lodging-related traits, including stem breaking resistance (SBR), stem diameter (SD), SS, and lodging coefficient (LC), were investigated among 472 rapeseed accessions. A genome-wide association study (GWAS) using Brassica 60K SNP array for stem lodging-related traits identified 67 significantly associated quantitative trait loci (QTLs) and 71 candidate genes. In parallel, a gene co-expression network based on transcriptome sequencing was constructed. The module associated with cellulose biosynthesis was highlighted. By integrating GWAS and gene co-expression network analysis, some promising candidate genes, such as ESKIMO1 (ESK1, BnaC08g26920D), CELLULOSE SYNTHASE 6 (CESA6, BnaA09g06990D), and FRAGILE FIBER 8 (FRA8, BnaC04g39510D), were prioritized for further research. These findings revealed the genetic basis underlying stem lodging and provided worthwhile QTLs and genes information for genetic improvement of stem lodging resistance in B. napus.